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Starting Fibonacci
Age 11 to 14
ShortChallenge Level 
Answer: 5
$\underline{\quad\quad\ }\quad\underline{\ \ \ \ 4\ \ \ \ }\quad\underline{\quad\quad\ }\quad\underline{\quad\quad\ }\quad\underline{\ \ \ 22\ \ \ }$
$\underline{\ \ \ x\ \ \ }\quad\underline{\ \ \ \ 4\ \ \ \ }\quad\underline{x+4}\quad\underline{x+8}\quad\underline{\ \ \ 22\ \ \ }$
$x+4\ \ +\ \ x+8\ \ =22\\
\Rightarrow 2x+12=22\\
\Rightarrow 2x=10\\
\Rightarrow x=5$
This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.
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